Electric switch



- Y 1945@ c. 1. HALL ET AL 53 ELECTRIC SWITCH Fil e d July 25, 1942 2 Sheets-Sheet 1 nventors: Chester" I. Hal I, Alexander W. BedFoPd,

Their Attorney.

May 28, 1946 Q HALL ET AL I 2,401,153

ELECTRIC swI'TcH Filed July-25, 1942 2 Sheets-Sheet? lnventovsz Chester I. Hal! 5 Alexander'- Their Attorney Patented May 28, 1946 ELECTRIC SWITCH Chester I. Hall, Rexford, and Alexander W. Bedford, Schenectady, N. Y., assignors to General Electric Company, a corporation of New York Application July 25, 1942, Serial No. 452,262

Claims.

Our invention relates to electric switches, more particularly to alternating current electric switches of the type known as contactors, and has for its object a simple and low cost electric switch, a switch which without the use of auxiliary arc extinguishing apparatus opens electric circuits carrying high currents at substantial voltages with no appreciable arcin between the contacts and, moreover, an electric switch whose operating parts and operation are unaffected by extremely heavy shocks or blows applied to the support on which the switch is mounted.

In conventional contactors such as used in the starting and the control of electric motors, the movable contact is operated by an electromagnet which when energized moves the movable contact into engagement with the stationary contact at a very high speed with destructive hammer blow effect between the contacts.

These contactors are opened by deenergization of the magnet or the release of a latch, and the movable contact moves to its open position at a very high speed and the contacts are widely separated so that a long are is established between them. This long arc supplies a relatively large amount of heat and is consequently diflicult to cool and extinguish. Consequently, it may reestablish itself each half cycle and persist for a number of cycles. The opening of such contactors under substantial current and voltage conditions is accomplished by violent electric explosive effects and considerable noise produced by this arcing between the contacts. Another disadvantage of conventional electromagnetically operated contactors is that they may be opened or closed by shocks or jars applied to the panel or support on which the contactor is mounted.

We have found that in the opening of electric circuits carrying substantial alternating currents at substantial voltages, such as the circuits of alternating current electric motors up to 100 H. P. or more at voltages of 440 or more, there is an optimum range of speed of movement of the movable contact with respect to the stationary contact within which the arcing between the contacts and destructiveness of this arcing is a minimum. This speed range at commercial frequencies of 60 cycles and voltages up to 600 is between the limits of .25 to 4 inches a second, although we prefer a speed within the limits of .5 to 1.5 inches a second. At contact speeds either lower or higher than this range, the destructiveness of the arc increases rapidly with decrease or increase in the contact speed.

In this optimum range of speed, the contacts have time to be separated a small distance only before the alternating current passes through the zero point of, its voltage wave. This is true even when the separation of the contacts begins soon after the zero point is passed and the contacts therefore continue to separate throughout substantially the entire half of the voltage wave up to the next zero point. In such case, arcin between the slightly separated contacts occurs but does no appreciable damage to the contacts because of the rapid cooling of the are by the close proximity of the contact surfaces. Thus current is conducted across such a very short gap with no detrimental effect. Also, such a short are is a low energy are and generates a relatively small amount of heat. When the zero point in the voltage wave is reached, however, the arc is extinguished because of lack of voltage and the separation of the contacts is then great enough to prevent reestablishment of the are as the voltage increases.

We have found that in a 550-volt, GO-cycle motor circuit a separation of the contacts of only two mils (.002") is sufiicient to prevent reestablishment of the arc. This is because the permissible voltage per mil of gap for very small or minute gaps is much higher than for relatively wide air gaps. Preferably, however, we continue the separation of the contacts to about .25 inch as a precaution against unusual conditions such as the accumulation of dirt on the contacts. In carrying out our invention, we preferably move the movable contacts to their closed circuit positions into engagement with the stationary contacts by means of an electric motor connected to drive the contacts at a suitable speed low enough to prevent hammer blows. This closing speed is high enough, however, to prevent any appreciable period of light pressure between the contacts, such as would cause welding of the contacts together because of the high electrical contact resistance and high heat generation. For opening of the contacts, we provide a spring which is wound up during the closing movement and which operates when the motor is deenergized to drive the motor backwards and open the contacts. The relation of the force applied by the spring to the inertia of the various parts driven by it is such that the contacts are opened at a predetermined optimum speed at which arcing is minimized.

Preferably also, we connect the motor to the movable contacts through a crank linkage which is on dead center when the contacts are either open or closed so that the operating mechanism is not affected by shocks and, therefore, the

switch can not be either opened or closed by such shocks.

We also provide manually operated means for closing or opening the contacts independently of the driving mechanism.

For a more complete understanding of our invention, reference should he had to the accompanying drawings, Fig. l of which is an exploded fragmentary view in perspective of a switch embodying our invention; Figs. 2, 3 are fragmentary views showing details of construction; Fig. 4 is a bottom view of Fig. 3; Fig. 5 is a plan view of a complete switch embodying the features of Figs. 1 to 4, inclusive; Fig. 6 is a side elevation view partly in section of Fig. 5; Fig. '7 is a sectional view along the line 1--1 of Fig. 5 looking in the direction of the arrows; Fig. 8 is a sectional view along the line 8-8 of Fig. 5 looking in the direction of the arrows; while Fig. 9 is a sectional view showing details of construction.

Referring to Fig. l of the drawings, in one form of our invention the movable contacts of the switch are mounted on an operating or cross bar In made of electrically insulating material, such as a, moulded compound, provided with a central cylindrical portion I l to which is secured one end of an operating link 12. This link or operating rod I2 is pivotally connected at its other end to a crank constituted by a pin i3 secured to a gear M a suitable distance from the pivot axis support for the gear. Thus rotation of the gear N moves the cylindrical portion H longitudinally and thereby moves the bar Ill between its closed and open circuit positions. Electric driving means shown as a rotary type electric motor I6 is connected to drive the gear l4 through a gear train comprising a gear ll mounted on the shaft 18 of the motor, a large gear [9 meshing with the gear ll, a shaft 20 to which the gear I9 is secured, and a small gear 2| secured on the shaft 20 and meshing with the ear M.

Preferably, the motor I6 is operated electrically in one direction only, and preferably also as shown in the drawing, this rotation of the motor moves the bar ID to its closed circuit position. When energized the motor turns the gear 14 through its gear train connection therewith to the position shown in the drawings in which the link l2 comes to rest against a flange 22 secured to the gear l4 whereby the gear M is stopped forcibly with the pin l3 in a dead center position with respect to the link [2,

As long as the switch is held. closed the motor remains energized and holds the gear M in this position.

For opening movement of the switch bar It! a spiral spring 23 is provided, constituting an energy storage device, the outside end of which is connected to a fixed post 24 and the inside end of which is connected to the shaft 20. This spiral spring is wound up by the clockwise rotation of the gear l9, looking down on Fig. 1, during the switch closing movement. Upon deenergization of the motor, the spring turns the gear 19 in a counterclockwise direction and thereby moves the gear train, the switch and the rotor of the motor to their open circuit positions. This open circuit position is again defined by the flange 22 which moves again into engagement with the link l2 although on the side of the link opposite that shown in Fig. 1 whereby the pin it is stopped in its opposite dead center position.

In order to effect the opening of the contacts at the predetermined desired slow speed with a minimum of arcing, which we have found to be a speed between .25 and i inches a second and preferably between .5" and 1.5" a second, the spring 23 is constructed to apply an opening force sufficient to give this desired rate of contact opening movement. It will be observed that, by reason of the fact that the pin [3 is in its dead center position when the switch is closed, the contact holding force applied through the link l2 does not assist the spring at the beginning of the opening movement. As the pin [3 moves away from the dead center position, a component of the contact holding force tends to rotate the gear M toward the open position and therefore assists the spring 23. Preferably, separation of the contacts begins after about movement of the gear M in a clockwise direction looking down on Fig. 1. At that time the spring has accelerated the ear and other driven parts to their maximum speeds. After rotation of the gear, it is brought to rest, as previously stated, by engagement of the flange 22 with the link l2.

For the purpose of absorbing the kinetic energy of the motor rotor and other moving parts in both the closed and open positions after the driving parts have been brought to rest by engagement of the flange 22 with the link [2, a friction clutch connection is provided between the shaft of the motor and the gear ll. This clutch consists of a disc 25 (Fig. 2) secured to the gear IT, a disc 26 secured to the motor shaft I8 and a suitable loose friction disc 21 between them. The gear I! is loose on the shaft l8 and is pressed by a spring 28 against th disc 25 whereby the gear is rotationally secured to the shaft by the friction between the discs. This friction is great enough to stop the rotor of the motor in one or two revolutions after the driving mechanism has come to rest. The friction should be as great as consistent with the strength of the parts driven by the motor in order to make available, in the event of welded contacts, as much as possible of the stored energy of the motor rotor.

As shown, the cross bar IIJ carries four bridging contact members 29, 30, 3| and 32, although in the control of a 3-phase motor, for example, only three of these will be used. These bridging members are secured at approximately their centers to the arm l0. Each carries a movable contact at each end cooperating with suitable stationary contacts 33 and 34 which are connected to suitable terminals for connection in the circuit of the electric motor or other device to be controlled.

We have found that in order to prevent arcing in the event of a weld between the contacts, the bridging members 29 and 32 and the other operating parts for the bridging members must be stiff and unyielding so as to break the weld without appreciable bending or flexing. In other words, the parts must be sufliciently stiff and unyielding to separate the welded contacts at the predetermined low speed. It will be obvious, on the other hand, that if the bridging members and other driving parts were resilient in the breaking of a weld, the movable contact immediately upon the breaking of the weld would snap away and move at a very high speed until the operating parts recovered their normal shapes. Such rapid opening movement by reason of the spring recovery action of the parts would result in destructive arcing between the contacts. Preferably, the bridging members are channel members for the purpose of increasing their rigidity.

The contact pressure is determined by the strength of a helical spring 35 (Fig. 6) mounted between each bridging member and the cross bar on the side of the bridging member opposite the movable contacts so as to be compressed during the final movement of the cross bar after engagement of the contacts. Each bridging member, as shown, extends through an aperture 36 provided for it in the cross bar. When the contacts are disengaged, the bridging member is held by the spring 35 on the seat for it formed by the lower or opposite Wall of the aperture 35. During the opening movement of each bridging member, it is held in its closed circuit position by the spring 35 as the cross bar I moves away until the cross bar NJ is rigidly engaged by the bridging member. Then the bridging member is forcibly moved away from the stationary contacts.

By means of a knob 31 the cross bar it, when in its open circuit position, can be latched in that position so that it can not be closed by the driving motor E or by shocks. Furthermore, when the cross bar is in its open circuit position, the knob 31 can be turned to release the cross bar from the link l2 and then the cross bar can be operated manually between its open and closed circuit positions and latched in its closed position as well as in its open position, as stated above, so that it can not be opened by the spring 23 or by shocks.

This knob 37 is secured to a sleeve 38 which is rotatably mounted in a longitudinal bore provided for it in the cylindrical member H, the center line of the sleeve 38 being coincident with the center line of the link l2. The link i2 extends into the sleeve 38 and is provided with a pin 39 which extends into a slot 40 in the sleeve. At each end as shown the slot 40 has a short transverse portion extending circumferentially of the sleeve while the main portion of the slot extends lengthwise of the sleeve. Normally the pin 39 lies in the right-hand transverse portion, Fig. 1, as shown, whereby the driving rod i2 is igidly connected to the cross bar Iii.

On the end of the sleeve 38 opposite the knob 31 is a transversely extending flange member 4| having two diametrically opposite projections 42 and 43 extending outward beyond the periphery of the supporting portion H. A spring 44 (Fig. 6) is provided in the knob which engages a hexagonal disc 45 secured to the end of the sleeve 38 thereby to bias the sleeve toward the left hand with respect to the knob, the disc 45 moving in a hexagonal seat in the knob, and hold the fiange 4| and the knob against opposite sides of the cylindrical portion ll. Furthermore, the cylindrical portion II extends loosely into a bore 56 (Fig. 6) provided for it in the stationary support 41 made of electrically insulating material on which the stationary contacts are secured.

Ordinarily, the projections 42 and 43 are free to move axially during movement of the cross bar I?) in slots 43 and 49 (Fig. 3) provided for them in opposite sides of the bore 59. If it is desired manually to close the switch, the switch at the time being open, the knob .31 is turned in a clockwise direction, as seen in Fig. 1, so as to bring the axial slot 40 into register with the pin 39 and then the knob is pushed inward on the rod [2 carrying with it the contact bar Hi to the closed position which brings the pin 39 to the left-hand end of the slot 40, as seen in Fig. 1, or rather the sleeve 33 is pushed inward until the end wall of the slot engages the projection 39. If it is desired to lock the switch in this closed position, the knob 31 is now turned still farther in a clockwise direction which is permitted by the outer lateral end portion of the slot 40 whereby the projections 42 and 43 move into the recesses 50 and 5| (Fig. 4) under the lower end of the wall of the bore 46 and latch the contact bar Iii in its closed circuit position. This manual closing operation compresses the helical spring 50a surrounding the link i2 and having one end bearing on the flange 4|. After thus being closed manually, the switch can be opened manually by the reverse operation of the knob, the spring 50a pushing the knob and cross bar Hi to their open positions.

The contact bar I!) may be latched in the open position after it has been moved by the motor 56 to the open position, by turning the knob to its extreme counterclockwise position as permitted by the much longer circumferential transverse end portion 51a of the slot at the righthand end of the slot 49, as seen in Fig. 1. This transverse portion of the slot 5m, together with the other transverse portion, provides for about degrees total rotation of the sleeve 38 and knob 37. It will be seen that when the bar ID has been moved to its open circuit position by the motor the lugs 42 and 43 are in position to be moved over the shoulders 52 and 53 simply by turning the knob 31 counterclockwise, whereby the contact bar is latched in its open position.

To facilitate the operation of the switch by the knob 37, the knob is provided with a periph eral dial flange on which suitable position marks numbered 1, 2, 3 and 4 are provided, these marks registering with a mark 5311 on the cross bar. With the dial in position as shown in Figs. 1 and 5, i. e., the No. 2 mark registering with the stationary mark 53a, the cross bar is operated normally by the motor [6. To move the cross bar to its closed circuit position and lock it as just described, the dial is turned to the position No. 3, pushed in and then turned still farther clockwise to the position No. 4. Counterclockwise rotation f the knob from position No. 2 of Fig. 5 to position No. l latches the cross bar in its open circuit position as just described. Moreover, the knob may be latched in any of these positions by providing a projection (not shown) on the inner side of the knob at each position and correspondhag depression for the projection in the cross bar l The above described releasable connection means between the cross bar l0 and the link l2, and the latching means whereby the cross bar can be secured in either its open circuit or closed circuit position, form no part of our invention and are described and claimed in a co-pending application S. N. 455,458, filed on August 20, 1942, by Edgar H, Ayers, and assigned to the same assignee as this invention.

As shown, the motor I6 is preferably a split phase motor having a capacitor 0r condenser 54 connected permanently in parallel with one of the motor windings.

A second capacitor 55 is connected in the circuit of the motor for the purpose of reducing the voltage applied to the motor after the motor has closed the switch so that the motor can remain energized on the supply circuit without overheating for indefinite periods of time. This capacitor 5-5 is short-circuited when the switch is in its open circuit position by means of an interlock switch operated by the gear [4. As shown in Fig. 1, the spring contact arm 56 of this interlock switch normally engages a stationary spring contact 53a thereby to short-circuit the capacitor 55. When the gear I4 is turned to the closed switch position, as shown in Fig. 1, a projection 51 on the flange 22 engages a pin 51a made of electrically insulating material, the other end of which engages the end of the spring contact arm 56. As the gear 14 completes its final movement to the open position, the pin 51a is moved to push the spring contact arm 56 away from the stationar contact and thereby open the short circuit around the capacitor '55. The motor It may be constructed, for example, for 80-vo1t alternating current continuously applied, but it may be operated on a much higher voltage from the alterhating current supply source 58, such as 440 volts, in the actual closing of the switch. This higher rate of voltage gives the motor a high rate of acceleration and the closing period of operation is so short that the motor is not overheated and damaged.

The operation of the switch arm 56 by the gear l4 assures that the short circuit around the capacitor 55 is opened only after the switch is closed and the motor M is nearly in its final closed position. At that time the pin I3 is closely approaching its dead center position shown in Fig. 1, and consequently the force applied to the gear by the operating rod l2 has only a very small component in opposition to the rotation of the gear by the motor, Thus the motor has enough torque under these conditions after the short circuit around the capacitor 55 is opened to complete the final closing movement of the gear M. This arrangement avoids the possibility of the opening of the short circuit around the condenser under conditions such that the motor can not complete the closing movement. Such conditions might occur if the short-circuit switch were operated by the cross bar l and a permanent electric connection were used in place of the push button 59, and a condition were encountered of slowly rising voltage on the supply circuit. In such case, the motor might operate back and forth to open and close the short-circuit switch repeatedly with opening and closing of the main switch contacts carried by the bar In.

When the capacitor 55 has been inserted in the motor circuit and the voltage of the motor thereby reduced, in the example shown to about 80 volts, the torque of the motor is enough to slightly more than overbalance the opening countertorque applied by the spring 23 to the shaft 20.

As shown, the motor circuit is closed by means of a normally open push button switch 59. This connects the motor directly to the supply source 58 through the normally closed stop push button 590., push button 59 and the interlock switch contacts 56 and 55a which at this time are in engagement with each other. The closing button 59 is held closed until the switch has been moved to its closed circuit position after which the button 59 may be released and allowed to open because it is then short-circuited by the interlock switch arm 60 operated by the cross bar l0. To open the switch the normally closed push button 59a is opened to deenergize the motor after which the switch is opened by the spring 23.

The speed of the contacts carried by the bridging members 29 to 32 inclusive at the instant of closing, i. e., engagement with the stationary contacts, is higher than the contact opening speed and is high enough to prevent welding of the contacts together because of high electrical contact resistance between them. Thus if the contacts are brought together at a very low relative speed, the high contact resistance between them caused by their low pressure of engagement may last long enough to cause welding of the contacts together. However, the closing speed is low enough to avoid destructive hammer blow action between the contacts.

It is contemplated that the device will be mounted in position on a panel or other support so that the bridging contact members 29 to 32 inclusive are substantially vertical. In this position it will be noted that each bridging member cooperates with a bottom stationary contact and a top stationary contact. The bar It! is furthermore operated in such manner that during the opening movement the bridging members disengage their top stationary contacts first and thereafter disengage their bottom stationary contacts. This sequence avoids the possibility of the lower contacts separating first and generating ionized gas which would rise and envelope the top contacts at the time they open. This effect would be especially pronounced in the event of heavy overloads.

The required tilting of the cross bar In about its longitudinal center line to effect this sequence in the opening of the top and bottom contacts is effected by means of the mechanical crank driving connection for the cross bar, Thus the device disclosed is mounted in a position such that the stationary contacts 34 (Fig. 1) are uppermost with the bridging contact members extending substantially vertically. In this device, the gear [4 was rotated about '70 degrees by the spring 23 to effect a separation of the top bridging contacts from the stationary contacts 34. It will be observed that the pin l3 in moving through this Iii-degree angle imparts an appreciable tilting action to the cross bar In through the operating connecting rod 12 because of the fact that the plane of rotary movement of the crank or gear 14 is substantially parallel with the planes of movement of the bridging contact members. In order to provide for this tilting of the cross bar, the bore 46 (Fig. 6) in the support 41 is made considerably larger at its right-hand end than the cylindrical portion ll of the cross bar extending into it. After this separation of the upper contacts, continued rotation of the gear i4 separates the lower contacts.

During the opening movement the springs 35, which are compressed in the closed circuit position, apply a component of force through the bar H to the gear M in the same direction as the force applied by the opening spring 23. This component of force becomes available after a slight movement of the gear M from the dead center position. As the gear I4 turns, this component of force of the springs 35 increases, although this may be oifset to a slight extent by the decreased pressure applied by the springs as they elongate. At the point of circuit opening, as previously stated, after the gear M has moved about 70 degrees, the gear I4 and other moving parts have been accelerated to a speed giving the desired optimum opening speed of the contacts. Of course, when the bridging contacts separate at one end from the stationary contacts, the force applied by the springs 35 to the rod I2 is materially decreased by reason of the fact that the cross bar has then been moved outward and tilted so that the edge at one end of each of the openings 36 engages a bridging contact. In other words, the bridging contacts become each seated at one end of its aperture 36. Thus after the circuit is open, the spring 23 is practically the sole operating means for the gear I l and other parts. Consequently, the gear I4 is accelerated to its maximum speed, as are also the other moving parts, before the contacts open and continues at that speed until the bridging contacts have been moved approximately to their full open circuit positions,

It will be observed that the engagement of the cross bar with the bridging contacts, the cross bar and other moving parts moving at their optimum speed, gives a hammer blow on the bridging contacts which is of value in the separation of the contacts in the event of a weld. The rotating parts, some of which, such as the rotor of the motor l6, rotate at quite high speeds, serve as energy inertia members or flywheel members and apply a powerful opening force to the cross bar.

Figs, 5 to 8, inclusive, show various additional structural details of an electric switch constructed as described in connection with Figs. 1 to 4, inclusive.

Referring to Figs, 5 and 6, the bridging contact members 29 to 32, inclusive, are shown as channel members whereby these members are made stiff enough to prevent their bending during the breaking of a weld between the contacts. With the switch in its closed circuit position, the bridging members as shown each have their ends resting on stationary contacts and the cross supporting bar Ill in moving still farther compresses the helical spring 35, Fig. 6, between the upper side of each bridging contact and the upper wall of the cross bar. These springs and the bridging contacts are held in position by a screw Bl extending through a hole in the cross bar and provided with a nut 62 which holds the screw or bolt in position and also forms a seat for the upper end of the sprin 35. The screw has an unthreaded portion at its lower end which extends loosely through an aperture in the middle of the bridging contact member so as to hold the bridging contact member against lengthwise movement with respect to the cross bar.

Figs. 5 to 8, inclusive, show the construction of the supporting member 41 made of insulating material on which is carried the stationary contacts, and also the construction of the cross bar It]. It will be observed that the support 41 is provided with a series of electrically insulating barrier walls separating the bridging members and stationary contacts. Thus the bridging member 29 is between two walls 63 and 64 formed as part of the support 41. Each of these walls, as shown in Fig. 8, is provided with a central notch 65 to receive the cross bar It). The cross bar likewise has arc walls 66 and 61 (Fig. 5) on opposite sides of the bridging contact 29 and overlapping, respectively, the slots or notches in the walls 63 and 64.

This electrically insulating support 4'5 has secured to it a rectangular metal wall 68 which forms a rectangular base for the support 4! and also encloses a space in which is mounted the motor l6 and the mechanism for opening and closing the switch. The motor is preferably secured as by screws (not shown) to opposite side Walls 68. Also in this space the two condensers 54 and 55 are mounted in a sealed compartment 68a from which three condenser terminals 58b. 68c and 68d are brought out. Three terminals only are required because of the fact that two terminals of the condensers are permanently connected together, as shown in Fig. 1.

Also mounted in this space of the metal wall 68 is the interlock switch constituted by the contact arms 56 and Etc, these contact arms bein suitably mounted in an electrically insulating support 68c shown in outline in Fig. 6. This support 586 is secured to the metal wall The construction of the interlock switch arm as is shown clearly in i It consist 5 air 1 of two spring contact arms which are shaped so as to move together at their upper ends thus in a closed position grasp the stationary contact 69 between them. The opposite ends of the arm 6d are mounted on a pivot 6911. This double contact arm til makes the interlock switch free from heavy lateral shocks for the reason that any such shock tending to move one or" the two contact arms away from the stationary contact at the same time must tend to move the other contact arm more tightly against the stationary contact. The contact arms are operatively connected to the cross bar it by providing a notch 5th in the end of the cross ba through which the contact arms extend. A similar interlock switch is arranged on the other end of the insulating support 51.

In order that the pin it will be strong enough to withstand heavy shocks, it is constructed as shown in Fig. 9 as an integral part of the upporting shaft 696! for the gear Hi. The pin l3 and the shaft 590! are machined from a single solid piece of hardened steel material. With this construction any shocks applied to the pin it are not transmitted to the gear id but are taken up by the bearing shaft (Edd. This construction makes possible tremendou strength by means of relatively small parts. The gear it may be cast on the hub portion to which the pin it! and shaft Eifid are secured, or it may be pressed on the hub.

While we have shown a particular embodiment of our invention, it will be understood, of course, that we do not wish to be limited thereto since many modifications may be made, and we therefore contemplate by the appended claims to cover any such modification as fall within the true spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. An electric switch comprising a pair of sta tionary contacts arranged with one contact substantially above the other contact, a bridging contact member, means supporting said bridging contact member in an upright position for movement into engagement with said stationary contacts, an operating rod substantially rigidly secured at one end to said supporting mean-s. crank means connected to the other end of said rod to operate said contact member, said crank means having its plane of movement substantially paralle1 with the plane of movement of said contact member so that said crank tilts said supporting means to disengage said contact member from said upper stationary contact before said lower stationary contact is disengaged. electric driving means connected to operate said crank when said driving means is energized to move said supporting means from said open cir cuit to said closed circuit position, and a spring connected to said crank so as to be wound up when said supporting mean is moved to said closed circuit position, said spring operating when said driving means is deenergized to turn said crank to an open circuit position.

2. An electric switch comprising a plurality of pairs of stationary contacts arranged With one contact of each pair substantially above the other contact, a plurality of bridging contact members, a cross bar supporting said bridging contact members in upright positions for movement of said contact members in substantially parallel planes into engagement with said pairs of stationary contacts, an operating rod substantially rigidly secured at one end to said cross bar, a crank for operating said rod having a plane of movement substantially parallel with the planes of movement of said contact members and movable from one dead center position to another to move said cross bar between circuit open and circuit closed positions, said crank tilting said cross bar so as to disengage said contact members from said upper stationary contacts before said lower stationary contacts are disengaged, electric driving means connected to operate said crank when said driving means is energized to move said cross bar from said open circuit to said closed circuit position, and a, spring connected to said crank so as to be wound up when said cross bar is moved to said closed circuit position, said spring operating when said driving means is deenergized to turn said crank to an open circuit position.

3. An electric switch comprising a support, a stationary contact on said support, a movable contact, an operating member for said movable contact mounted for slidable movement, a crank, a rod connecting said crank to said operating member to move said operating member between closed and open circuit positions upon rotation of said crank, said crank being in a substantially dead center position when said operating member is in each of said positions, electric means for rotating said crank between said dead center positions when said electric means is energized, means for stopping said crank at each of said dead center positions, energy storing means connected to said operating member for moving said member upon deenergization of said electric means to its open position at a predetermined substantially uniform low speed at which alternating current arcing is minimized, and manual means for releasing said operating member from said rod and for thereafter moving said oper atlng member with relation to said rod and locking said operating member to said support in one of said positions.

4. An electric switch comprising a support, a stationary contact on said support, a movable contact, an operating member for said movable contact, a crank, a driving connection between said crank and said operating member for moving said operating member between closed and open circuit positions upon rotation of said crank, said crank being in a substantially dead center position when said operating member is in each of said positions, electric means for turning said crank to one of said dead center positions when said electric means is energized, means for stopping said crank in each of said dead center positions, energy storing means connected to said crank for turning said crank to said other dead center position upon deenergization of said electric means, and means for releasing said. operating member from said crank and for locking said operating member to said support in one of said positions.

5. An electric switch comprising at least two stationary contacts, a bridging contact member, means supportin said bridging contact member for movement between two positions to bring opposite ends of said contact member into engaged and disengaged relation with said stationary contacts, an operating rod substantially rigidly secured at one end to said supporting means, crank means connected to the other end of said rod for operating said contact member, said crank means havin its plane of movement substantially parallel with the plane of movement of said contact member so that said crank means tilts said contact member through said operating rod thereby to disengage one end of said contact member from one of said stationary contacts belor the other end of said contact member is disengaged from the other of said stationary contacts, and means for driving said crank means to move said contact member between engaged and disengaged positions with respect to said stationary contact.

CHESTER I. HALL. ALEXANDER W. BEDFORD. 

